FIG. 1 depicts a portion of a conventional magnetic transducer 10, such as a conventional read transducer or other device. The conventional transducer 10 resides on a conventional substrate 11, such as an AlTiC substrate. The conventional transducer 10 includes a conventional bottom shield 12, conventional sensor 20, and conventional top shield 40. The transducer 10 also typically includes seed layer(s) (not shown) between the conventional AFM layer 22 and the conventional shield 12. The conventional shields 12 and 40 typically include NiFe and are formed by plating. The sensor 20 is shown in a current-perpendicular to plane (CPP) configuration. In a CPP configuration, read current is driven generally perpendicular to the plane of the layers of the device, along the z-axis shown.
The conventional sensor 20 includes a conventional antiferromagnetic (AFM) layer 22, a conventional synthetic antiferromagnet (SAF) 24, a conventional barrier layer 32, a conventional free layer 34, and may include a conventional capping layer 36. The conventional free layer 34 has a magnetization that is substantially free to change direction in response to an applied magnetic field, for example from a bit being read. The conventional barrier layer 32 may allow conduction through the sensor 20 via tunneling. The sensor 20 is thus a tunneling magnetoresistive (TMR) sensor. Note that if a conductive spacer layer is used instead of the barrier layer 32, then the sensor 20 is a spin valve. The conventional SAF layer 24 typically includes two ferromagnetic layers 26 and 30 separated by a nonmagnetic spacer layer 28. The ferromagnetic layers are generally antiferromagnetically coupled. The magnetization(s) of the conventional SAF layer 24 are pinned by the conventional AFM layer 22. More specifically, the first ferromagnetic layer 26, typically termed the pinned layer, has its magnetization pinned by the conventional AFM layer 22, for example via exchange interaction. The remaining ferromagnetic layer, or reference layer 30, has its magnetization pinned because it is strongly magnetically coupled with the pinned layer 26. The conventional pinned layer 26 is typically a single layer, for example composed of Co90Fe10. Other conventional pinned layers 26 may be composed of Co75Fe25.
Although the conventional sensor 20 functions, the conventional transducer 10 may have limited utility. For example, baseline popping (BLP) and/or baseline line noise (BLN) may occur in the conventional read sensor 20 when used in a CPP configuration. BLP refers to time domain random noise spikes above the noise baseline. BLN refers to high overall noise baseline. Both BLP and BLN are of large frequency bandwidth, generally ranging from KHz to GHz. The presence of the BLP and BLN adversely affect the signal to noise ratio, and thus performance, of the conventional transducer 10. BLP and BLN may also be significant failure modes in hard disk drive applications of the conventional sensor 20. Because they may be failure modes, BLN and BLP may also adversely affect reliability of the conventional sensor 20. Thus, use of the conventional transducer 10 may have drawbacks.
Accordingly, what is needed is a system and method for providing a transducer having improved performance.